无法在GCC 9.2中链接libpqxx

Question

我尝试编译简单程序。

main.cpp：

#include <iostream>

#include <pqxx/pqxx>

using namespace std;

int main(int argc, char **argv)
{

    pqxx::connection conn("postgresql://root@localhost/company");

    return 0;
}

CMakeLists.txt：

cmake_minimum_required(VERSION 3.12)

project(TestProject)

include_directories("/usr/local/Cellar/gcc/9.2.0/include")
link_directories("/usr/local/Cellar/gcc/9.2.0/lib")


set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17 -lpqxx -lpq")
set(CXX_STANDARD_REQUIRED 17)

add_executable(testPQ main.cpp)
target_include_directories(testPQ PRIVATE "/usr/local/Cellar/libpqxx/6.4.5_1/include" "/usr/local/Cellar/libpq/11.4/include")
target_link_directories(testPQ PRIVATE "/usr/local/Cellar/libpqxx/6.4.5_1/lib" "/usr/local/Cellar/libpq/11.4/lib")
target_link_libraries(testPQ "libpqxx.dylib" "libpq.dylib")

我收到以下错误消息：

Undefined symbols for architecture x86_64:
  "pqxx::connectionpolicy::connectionpolicy(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)", referenced from:
      pqxx::connect_direct::connect_direct(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) in main.cpp.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make[2]: *** [testPQ] Error 1
make[1]: *** [CMakeFiles/testPQ.dir/all] Error 2
make: *** [all] Error 2

GCC版本：9.2； LIBPQXX版本：6.4.5;作业系统：OS X 10.14; CMake版本：3.15.1

但是CommandLineTools的GCC（Apple LLVM版本10.0.1（clang-1001.0.46.4））将其编译成功。